blob: d4ab1a998f6052a2aa74fce972e013088f4a8fc0 [file] [log] [blame]
package terraform
import (
"fmt"
"github.com/hashicorp/hcl/v2"
"github.com/hashicorp/terraform/internal/tfdiags"
"github.com/zclconf/go-cty/cty"
"github.com/zclconf/go-cty/cty/gocty"
)
// evaluateCountExpression is our standard mechanism for interpreting an
// expression given for a "count" argument on a resource or a module. This
// should be called during expansion in order to determine the final count
// value.
//
// evaluateCountExpression differs from evaluateCountExpressionValue by
// returning an error if the count value is not known, and converting the
// cty.Value to an integer.
func evaluateCountExpression(expr hcl.Expression, ctx EvalContext) (int, tfdiags.Diagnostics) {
countVal, diags := evaluateCountExpressionValue(expr, ctx)
if !countVal.IsKnown() {
// Currently this is a rather bad outcome from a UX standpoint, since we have
// no real mechanism to deal with this situation and all we can do is produce
// an error message.
// FIXME: In future, implement a built-in mechanism for deferring changes that
// can't yet be predicted, and use it to guide the user through several
// plan/apply steps until the desired configuration is eventually reached.
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Invalid count argument",
Detail: `The "count" value depends on resource attributes that cannot be determined until apply, so Terraform cannot predict how many instances will be created. To work around this, use the -target argument to first apply only the resources that the count depends on.`,
Subject: expr.Range().Ptr(),
// TODO: Also populate Expression and EvalContext in here, but
// we can't easily do that right now because the hcl.EvalContext
// (which is not the same as the ctx we have in scope here) is
// hidden away inside evaluateCountExpressionValue.
Extra: diagnosticCausedByUnknown(true),
})
}
if countVal.IsNull() || !countVal.IsKnown() {
return -1, diags
}
count, _ := countVal.AsBigFloat().Int64()
return int(count), diags
}
// evaluateCountExpressionValue is like evaluateCountExpression
// except that it returns a cty.Value which must be a cty.Number and can be
// unknown.
func evaluateCountExpressionValue(expr hcl.Expression, ctx EvalContext) (cty.Value, tfdiags.Diagnostics) {
var diags tfdiags.Diagnostics
nullCount := cty.NullVal(cty.Number)
if expr == nil {
return nullCount, nil
}
countVal, countDiags := ctx.EvaluateExpr(expr, cty.Number, nil)
diags = diags.Append(countDiags)
if diags.HasErrors() {
return nullCount, diags
}
// Unmark the count value, sensitive values are allowed in count but not for_each,
// as using it here will not disclose the sensitive value
countVal, _ = countVal.Unmark()
switch {
case countVal.IsNull():
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Invalid count argument",
Detail: `The given "count" argument value is null. An integer is required.`,
Subject: expr.Range().Ptr(),
})
return nullCount, diags
case !countVal.IsKnown():
return cty.UnknownVal(cty.Number), diags
}
var count int
err := gocty.FromCtyValue(countVal, &count)
if err != nil {
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Invalid count argument",
Detail: fmt.Sprintf(`The given "count" argument value is unsuitable: %s.`, err),
Subject: expr.Range().Ptr(),
})
return nullCount, diags
}
if count < 0 {
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Invalid count argument",
Detail: `The given "count" argument value is unsuitable: must be greater than or equal to zero.`,
Subject: expr.Range().Ptr(),
})
return nullCount, diags
}
return countVal, diags
}